Semiconductor process chamber having improved gas distributor

ABSTRACT

A process chamber  25  for processing a semiconductor substrate, comprises a support for supporting a substrate  50.  A gas distributor  90  provided for introducing process gas into the chamber  25,  comprises a gas nozzle for injecting process gas at an inclined angle relative to a plane of the substrate  50,  into the chamber  25.  Optionally, a gas flow controller  100  controls and pulses the flow of process gas through one or more gas nozzles  140.  An exhaust is used to exhaust the process gas from the chamber  25.

CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.09/086,704, filed on May 28, 1998, now U.S. Pat. No. 6,185,839, entitled“Semiconductor Process Chamber Having Improved Gas Distributor” which isincorporated herein by reference in its entirety.

BACKGROUND

This invention relates to a process chamber for processing semiconductorsubstrates, and in particular to a gas distributor for distributingprocess gas into the process chamber.

A process gas distributor that provides a non-uniform distribution ofprocess gas in a process chamber can cause large variations inprocessing rates and uniformity across a surface of a substrateprocessed in the chamber. In semiconductor fabrication, process gas isintroduced into the chamber and a plasma is formed from the process gasto etch or deposit material on the substrate. However, currentsemiconductor substrates have increased in diameter from 100 mm (4inches) to 300 mm (12 inches). The proportionate increase in the volumeof the chamber has made it more difficult to provide a uniformdistribution of process gas or plasma species across the entireprocessing surface of the substrate. As a result, there is oftenconsiderable variation in processing rates and processing uniformityfrom the center to the periphery of the substrate.

Achieving a uniform process gas distribution is a particular problem inprocess chambers having ceramic walls or ceilings because it isdifficult to fabricate the ceramic components with feed-throughs thatallow gas nozzles to extend therethrough to uniformly distribute processgas into the process chamber. The ceramic walls are composed ofpolycrystalline ceramic material, such as aluminum oxide or silicon,which are brittle materials and difficult to machine holes for holding agas feedthrough without breaking or otherwise damaging the ceramiccomponent. Also, other components, such as RF induction coils, adjacentto the ceramic walls further reduce the space available for locating agas nozzle through the wall. Thus there is a need for a gas distributorthat provides a uniform distribution of process gas in a process chamberhaving ceramic walls or ceilings without requiring a hole or otherfeed-through to be drilled through the ceramic component.

Yet another problem with current process chambers is that a relativelylarge amount of process gas is required to provide uniform processingrates across the substrate as compared to the amount of process gasactually consumed during processing of the substrate. Conventionalprocess chambers require an abundance of process gas to assure completeprocessing of the semiconductor substrates. For example, typical CVDprocesses are 30 to 68% efficient, which leaves 70 to 32% of theunconsumed process gas exhausted in the effluent gas. Typical etchprocesses are even less efficient and often use as little as 10% of thetotal volume of process gas. These inefficiencies in process gasutilization increase the processing cost per substrate, particularlywhen the process gas is expensive. Also, excessive emissions ofunconsumed process gases necessitate some form of effluent abatementapparatus to reduce the toxic or environmentally hazardous compounds inthe effluent process gas, which is also expensive.

Thus there is a need for a process chamber having a gas distributor thatprovides a uniform distribution of process gas in the chamber,particularly for large diameter substrates. There is a further need fora gas distributor that increases the efficiency of utilization ofprocess gas in the chamber, and thereby reduces environmentallyhazardous emissions. There is also a need for a gas distributor thatdoes not require holes or feed-throughs in ceramic walls in order toprovide a uniform distribution of gas in the chamber.

SUMMARY

In one aspect of the invention a substrate processing method comprisessupporting a substrate in a process zone; directing a flow of processgas against a surface above the process zone; before or after theprevious step, energizing the process gas; and exhausting the processgas from the process zone.

In another aspect of the invention, a substrate processing methodcomprises supporting a substrate in a process zone; introducing processgas at an inclined angle relative to the substrate to direct a flow ofthe process gas toward a surface adjacent the process zone; before orafter the previous step, energizing the process gas; and exhausting theprocess gas from the process zone.

In another aspect of the invention, a substrate processing methodcomprises supporting a substrate in a process zone; introducing processgas though a plurality of outlets at an inclined angle relative to thesubstrate, the inclined angle being sufficiently large to allow twostreams of process gas to impinge against one another; before or afterthe previous step, energizing the process gas; and exhausting theprocess gas from the process zone.

In another aspect of the invention, a substrate processing methodcomprises supporting a substrate in a process zone; introducing processgas through a first outlet at an inclined angle relative to thesubstrate and through a second outlet angled relative to the firstoutlet; before or after the previous step, energizing the process gas;and exhausting the process gas from the process zone.

In another aspect of the invention, a substrate processing methodcomprises supporting a substrate in a process zone; introducing processgas at an inclined angle relative to the substrate from above thesubstrate; before or after the previous step, energizing the processgas; and exhausting the process gas from the process zone.

In another aspect of the invention, a substrate processing methodcomprises supporting a substrate in a process zone; introducing processgas alternately through a plurality of outlets; before or after theprevious step, energizing the process gas; and exhausting the processgas from the process zone.

Finally, in another aspect of the invention, a substrate processingmethod comprises supporting a substrate in a process zone; introducing afirst burst of process gas into the process zone through a first nozzleand energizing the process gas; and introducing a second burst ofprocess gas into the process zone through a second gas nozzle whilecontinuing to energize the process gas.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings which illustrateexamples of preferred embodiments of the invention, where:

FIG. 1 is a schematic sectional side view of a process chamber andprocess gas distributor of the present invention;

FIG. 2a is a schematic sectional side view of the process chamber andprocess gas distributor of the present invention showing the gas flowpaths;

FIG. 2b is a schematic sectional top view of the process chamber of FIG.2a;

FIGS. 3a to 3 c are graphical representations of gas flow timingsequences for actuating flow controllers for supplying process gas tothe gas nozzles;

FIG. 4 is an illustrative block diagram of computer program productaccording to the present invention;

FIG. 5a is a contour map of etch rates of a blanket layer of aluminum ona substrate that is etched in a chamber having gas nozzles inclined atan angle of 45°;

FIG. 5b is a three-dimensional graph of the etch rates according to thecontour map shown in FIG. 5a;

FIG. 6a is a contour map of the etch rates of a blanket layer ofaluminum on a substrate that is etched in a chamber having gas nozzlesinclined at an angle of 60°;

FIG. 6b is a three-dimensional graph of the etch rates according to thecontour map shown in FIG. 6a;

FIG. 7a is a contour map of the etch rates of a blanket layer ofaluminum on a substrate that is etched in a chamber having gas nozzlesinclined at an angle of 75°; and

FIG. 7b is a three-dimensional graph of the etch rates according to thecontour map shown in FIG. 7a.

DESCRIPTION

The process chamber of the present invention processes a semiconductorsubstrate using a gas distribution system capable of providing a moreuniform distribution of process gas in the process chamber. An exemplaryapparatus 20 of the present invention is schematically illustrated inFIG. 1, is provided only to illustrate an example of the presentinvention, and should not be used to limit the scope of the invention.The apparatus 20 generally comprises an enclosed chamber 25 havingsidewalls 30, a bottom wall 35, and a ceiling 40. The chamber 25 isfabricated from any one of a variety of materials including metals,ceramics, glasses, polymers, and composite materials. Metals commonlyused to fabricate the process chamber 25 include, for example, anodizedaluminum, stainless steel, or INCONEL™, of which anodized aluminum ispreferred. Ceramic and semiconductor materials that can be used tofabricate the chamber 25 include, for example, silicon, boron carbide,and aluminum oxide.

The process chamber 25 comprises a pedestal or support 45 at the bottomof the chamber 25 for supporting the substrate 50 thereon. Preferably, adielectric member 55 positioned on the support 45 has a receivingsurface 60 for receiving the substrate. The dielectric member 55comprises a unitary monolithic structure of ceramic or polymer, forexample, aluminum oxide or aluminum nitride, with an electrode 65embedded in the dielectric member 55. Preferably, the electrode 65 isfabricated from a conductive high melting point refractory metal, suchas tungsten, tantalum, or molybdenum. As illustrated in FIG. 1, thedielectric member 55 also comprises gas feed-through holes 70 forproviding heat transfer gas, such as helium, to the receiving surface 60below the substrate. Typically, a series of gas feed-through holes 70are provided around the circumference of the dielectric member 55 toprovide a uniform distribution of heat transfer gas in the region belowthe substrate 50.

The electrode 65 in the dielectric member 55 has dual functions, servingboth as a gas energizer 72 or plasma generator for energizing andsustaining a plasma from the process gas in the chamber 25 bycapacitively coupling to an electrically biased or grounded surface ofthe chamber 25, and also as an electrostatic chuck that generates anelectrostatic charge for electrostatically holding the substrate 50. Anelectrode voltage supply 75 maintains an electrical potential betweenthe electrode 65 and a surface of the chamber 25, such as the ceiling40. Preferably, both a DC chucking voltage and an RF bias voltage areapplied to the electrode 65 through an electrical connector. The RF biasvoltage comprises one or more frequencies from 13.56 MHZ to 400 KHz at apower level of from about 50 to about 3000 Watts. The DC voltage istypically from about 250 to about 2000 volts, and is applied to theelectrode 65 to generate electrostatic charge that holds the substrate50.

The apparatus 20 comprises a dome-shaped ceiling 40 that serves as awindow for coupling an RF induction field transmitted by an inductorantenna 80 adjacent to the ceiling 40 to energize the process gas in thechamber. By dome shaped it is meant a single or multiple radius dome,planar, conical, truncated conical, cylindrical, multi-sided polyhedralshaped ceiling member, or combination of such shapes. Preferably, theinductor antenna 80 comprises multiple coils having a circular symmetrywith a central axis coincident with the longitudinal axis of the processchamber 25 and perpendicular to the plane of the substrate 50. Thecircular symmetry of the multiple coils provides a spatial distributionof inductive electrical field vector components that have a null orminimum along the central axis of symmetry to reduce the number ofelectrons over the center of the substrate 50, as described in U.S.patent application Ser. No. 08/648,254, which is incorporated herein byreference. Preferably, each coil comprises from about 1 to about 10turns, and more typically from about 2 to about 6 turns.

In one version, the ceiling 40 is made from dielectric or semiconductingmaterial that has a low impedance to the RF induction field of theinductor antenna 80, and has an electric field susceptibility that issufficiently low to transmit the RF induction field generated by theinductor antenna 80 through the ceiling 40 with minimum loss of power.For example, the ceiling can be made from aluminum oxide that istransparent to RF induction fields. The ceiling 40 can also be made frommetal or semiconductor material, and maintained at an electricalpotential or electrical ground. Typically, an RF source power supply 85powers the inductor antenna 80, and the electrode voltage supply 75biases the electrode 65 relative to the ceiling 40. Instead of theelectrode 65 or the inductor antenna 80, the gas energizer 72 can alsocomprise a microwave or other source of ionizing radiation capable ofenergizing the process gas before or after injection into the processchamber.

The process gas and process gas byproducts that are formed duringprocessing of the substrate are exhausted by an exhaust system 115comprising exhaust pumps 120 (typically including a 1000 liter/sec turbomolecular pump and roughing pump) with a throttle valve 125 in theexhaust line to control the pressure of process gas in the chamber 25.Preferably, an annulus surrounding the lower portion of the chamber 25forms an asymmetric pumping channel 130 for pumping gas out of thechamber 25 to provide a more uniform distribution of gaseous speciesaround the surface of the substrate. The interior of the asymmetricpumping channel 130 is lined with a replaceable metal liner 135 tofacilitate removal and cleaning of residue formed on the annulus.

To process the substrate, process gas is introduced into the chamber 25through a gas distributor 90 (or gas distribution system) of the presentinvention that generally includes a process gas supply 95, a gas flowcontroller 100 that operates mass flow controllers 105 that control theflow of gas through a gas feed conduit 110, and one or more gasinjection nozzles 140 that direct the flow of process gas into thechamber 25. The process gas supply 95 comprises a conventional gassupply, such as a tank of compressed process gas. The gas flowcontroller 100 controls the flow of process gas and typically comprisesa computer controller system 145 and computer program that operates themass flow controllers 105 and/or pneumatic or solenoid valves 150 ineach gas feed conduit 110 that extends to a particular gas nozzle 140.Preferably, the gas feed conduit 110 extends through the sidewalls 30 ofthe chamber 25 so that holes or other feed-throughs do not have to bemachined through the ceiling 40.

The gas nozzles or outlet 140 comprise a single gas nozzle or morepreferably a plurality of gas nozzles or outlets 140 a,b,c,d.Preferably, the multiple gas nozzle version comprises pairs of gasnozzles 140 a,b that face each other across the diameter of the chamber25. In the paired configuration, a first gas nozzle 140 a injects afirst gas stream at an inclined angle relative to a plane of thesubstrate 50 into the chamber 25; and a second gas nozzle 140 b facingthe first gas nozzle 140 a, injects a second gas stream also at aninclined angle relative to the plane of the substrate 50. While a singlepair of facing inclined gas nozzles 140 a,b can be used, it is preferredto have multiple pairs of gas nozzles 140 a,b and 140 c,d, as shown inFIG. 1. More preferably, the multiple facing pairs of gas nozzles 140a,b,c,d comprises one or more groups of gas nozzles 140 that are spacedapart and positioned around the periphery of the substrate 50 to providea uniform flux of process gas entering the chamber 25 from around theperiphery of the substrate 50. In a preferred embodiment, the gasdistributor 90 comprises at least four to eight gas nozzles 140 spacedapart and positioned symmetrically at 90° or 45° intervals around thecircumference of the chamber 25 to inject process gas uniformly into theentire process chamber.

Preferably, at least one group of first and second gas nozzles 140 a,binject first and second gas streams at an inclined angle relative to theplane of the substrate 50. The angle at which the gas streams areinjected is sufficiently large to cause the first and second gas streamsto impinge against one another and form a circulating gas flow streamthat rises to the ceiling 40 above the center of the substrate 50 anddescends along the periphery of the substrate 50, as illustrated by thegas flow path lines of FIGS. 2a and 2 b. Preferably, the gas nozzles 140are positioned in an inclined surface of an annular collar 148 or in thesidewalls 30 of the chamber 25. Each outlet of the gas nozzles 140comprises a longitudinal channel having a central axis that forms aninclined upward angle relative to the plane of the substrate 50, topropel the gas stream toward the ceiling 40 of the chamber 25. It hasalso been discovered that a preferred angle of inclination for thelongitudinal channel which determines the angle of inclination of acentral axis of the gas streams flowing into the chamber is from about30 to about 80°, and more preferably from about 40 to about 60°. Atthese angles, the gas streams from the gas nozzles 140 have been foundto provide a circulating gas flow pattern that provides a uniformdistribution of process gas across the surface of the substrate 50 andsignificantly improves substrate yields.

In a preferred embodiment, the gas distributor 90 comprises a firstgroup of facing inclined gas nozzles 140 a,b that inject gas streams atan inclined angle relative to the plane of the substrate 50, and asecond group of facing non-inclined gas nozzles 140 c,d that injects gasstream in a plane that is substantially parallel to the plane of thesubstrate 50. In a preferred configuration, the gas nozzles 140 aremounted in the annular collar 148 that extends around the circumferenceof the chamber 25. The collar 148 has an inclined surface containing thegroup of inclined gas nozzles 140 a,b that inject gas at an inclinedangle into the chamber 25 and a perpendicular surface containing thegroup of directly opposing gas nozzles 140 c,d that inject gas parallelto the plane of the substrate 50. The annular collar 148 provides asmooth and flat surface for containing the gas nozzles 140 from whichresidue deposits can be easily cleaned, and also serves to contain theprocess gas about the substrate. The annular collar 148 can be machinedfrom a block or segmented blocks of ceramic material or metal material,that contain the conduits and outlets of the gas nozzles 140.

In operation, the inclined gas nozzles 140 a,b inject their gas streamsat an inclined angle, causing the inclined gas streams to impingeagainst one another, coalesce, and form a combined gas stream that risesabove the center of the substrate 50, strikes the opposing ceiling 40 orother surface of the chamber 25, and descends along the periphery of thesubstrate 50. The opposing gas nozzles 140 c,d that inject their gasstreams directly against one another cause their gas streams to impingedirectly above the center of the substrate 50 so that a portion of thecombined gas stream descends on the center of the substrate 50 andanother portion of the gas stream rises up above the center of thesubstrate 50. The combination of gas streams rising upwardly anddownwardly across the center and periphery of the substrate provide agas distribution across the chamber 25 that results in uniformprocessing rates across the entire surface of the substrate 50. Thenumber and angle of inclination of the inclined gas nozzles 140 a,b andthe number of the opposing gas nozzles 140 c,d depends on the size ofthe process chamber and the volumetric flow rate of process gas throughthe gas nozzles 140. Although described as two groups of gas nozzles,the gas distributor 90 can also comprise a plurality of groups ofinclined and non-inclined gas nozzles 140, each group of gas nozzlesbeing inclined at a different angle relative to the plane of thesubstrate 50 or relative to the shape of the surface of the ceiling 40.Preferably, the groups of gas nozzles 140 are positioned symmetricallyto one another in the chamber 25, and are spaced apart at equalintervals along the chamber to alternate position the inclined gasnozzles 140 a,b and non-inclined gas nozzles 140 c,d.

The circulating gas flow streams provided by the facing gas nozzles 140works particularly efficiently in combination with a curved chambersurface, such as the domed shaped ceiling 40 that faces and opposes theprocessing surface of the substrate 50. In this version, the upwardlymoving gas stream above the center of the substrate 50 strikes thechamber ceiling 40 and is redirected in a circular flow path by thecurved ceiling 40 toward the periphery of the substrate 50. Preferably,the curved ceiling 40 comprises an average radius of curvature that issufficiently large to direct the upwardly rising gas stream downward andtoward the periphery of the substrate 50. The domed ceiling 40preferably comprises a multiradius dome having multiple radii ofcurvature with a mean or average radius of curvature of at least about150 mm. Other facing curved surfaces having an apex, such as conical orother radially symmetric or concentric shapes, can also be used toredirect the process gas in the chamber 25. The process gas flow pathredirected by the curved ceiling 40 provides a more uniform distributionof process gas species across the surface of the substrate 50 and betteretching or deposition process uniformity across the substrate surface.

To process a substrate, the process chamber 25 is evacuated andmaintained at a predetermined subatmospheric pressure. The substrate 50is then deposited on the support 45 by a robot arm and lift pin system(not shown). The electrode 65 is electrically biased with respect to thesubstrate 50 by an electrical voltage. Process gas that is introducedinto the process chamber 25 via the gas nozzles 140 is energized to forman energized process gas or plasma by maintaining coupling RF energyinto the chamber 25 using coils and/or electrically biased processelectrodes. FIGS. 2a and 2 b illustrate the gas flow lines in theprocess chamber 25 showing that the process gas rises up toward theceiling 40, flows downward along the periphery of the substrate 50, andthen flows into the asymmetric channel 130 of the exhaust system 115.Fresh process gas enters the process chamber 25 via the inclined oropposite facing gas nozzles 140 and circulates in a radially symmetricalgas flow path. Even though the gas nozzles 140 are located along thecircumference of the sidewalls 30 of the chamber 25, the resultantcircular or elliptical gas flow path simulates a gas flow stream thatwould occur from a gas distributor that extends gas nozzles through theceiling 40 because at least a portion of the gas stream inside thechamber flows from the top of the chamber down towards the sides of thechamber walls. Also, because the gas flow path is from the top of thechamber 25 and downward toward the substrate, there is lesscontamination of the substrate 50 by etchant residue and particulatesthat otherwise flake off from around the substrate or gas nozzles 140.The resultant increased relative pressure of gas immediately above thesubstrate 50 provides an enhanced uniformity of processing rates acrossthe substrate 50 and uses less process gas to process the substrate 50.As a result, smaller amounts of process gas are released in the gaseouseffluent to provide more environmentally safe processing.

The apparatus 20 described herein can be used to deposit material on asubstrate 50 such as by chemical vapor deposition, etch material fromthe substrate, or clean contaminant deposits deposited on walls andcomponents in the chamber 25. Typical chemical vapor depositionprocesses that can be performed to deposit coatings on a substrate 25are generally described in Chapter 9, VLSI Technology, 2nd Ed., Ed. bySze, McGraw-Hill Publishing Co., New York, which is incorporated hereinby this reference. For example, SiO₂ is deposited by a process gascomprising (i) silicon source gas for example SiH₄ or SiCl₂H₂, and anoxygen source gas such as CO₂ and H₂O, or N₂O; or (ii) a single gascontaining both silicon and oxygen such as Si(OC₂H₅)₄. Otherconventional CVD process gases include NH₃, N₂, AsH₃, B₂H₆, KCl, PH₃,WF₆, and SiH₄. The apparatus 20 can also be used for other etchingprocesses as generally described in VLSI Technology, Second Edition,Chapter 5, by S. M. Sze, McGraw-Hill Publishing Company (1988), which isincorporated herein by reference. Typical processes or etching metallayers use process gases such as BCl₃, Cl₂, SF₆, CF₄, CFCl₃, CF₂Cl₂,CF₃Cl, CHF₃ and C₂ClF₅. Resist etching processes typically use oxygengas to etch the polymeric resist on the substrate 50.

In any of the embodiments described herein, the process gas can alsocomprise a neutral or non-reactive carrier gas that is added to thereactive gases in a volume percent ratio of about 20 to about 80 volume%, and more preferably from 40 to 70 volume %. The carrier gas furtherreduces the volume of the process gas that is used for processing thesubstrate 50 and also further reduces emissions of toxic or hazardousgases in the effluent. The carrier gas serves to transport the activegas species past the substrate surface to maximize the amount of carriergas that reacts with the substrate 50. The carrier gas operatesparticularly efficiently in conjunction with the gas distributor 90 byefficiently transporting reactive gaseous species throughout the chamber25 and evenly past the processing surface of substrate 50.

The process chamber 25 of the present invention provides significantlyimproved processing uniformity. It is believed that these results occurbecause theoretical diffusive gas flow does not occur in all chambersoperated at low chamber pressures, as commonly believed in the art. Ithas been discovered that in some regions the process gas diffusesthrough the chamber, and in other regions, steady state flow patterns ofprocess gas occur during processing. The steady state flow patternsaffect the distribution of gas species and the processing uniformity ofthe substrate surface. The gas flow distributor 90 of the presentinvention provides steady state gas flow streams that result in a moreuniform distribution of gaseous species in the chamber 25 and enhancedprocessing uniformity. The gas flow streams also reduce gas stagnationregions and prevent excessive deposition of process residues on chamberwalls and on the substrate 50. The gas flow stream across the surface ofthe substrate 50 also provides more efficient utilization of the processgas thereby decreasing hazardous or toxic gas in the effluent gas.

In another aspect of the present invention, the flow of process gas intothe chamber 25 is regulated to provide pulsed bursts of process gas intothe chamber 25. In this aspect, the flow of process gas to a gas nozzle140 is turned on and thereafter turned off, while processing a substrate50, to provide short pulsed bursts of gas into the chamber 25. The gasflow controller 100 regulates the flow of process gas through one gasnozzle 140 or groups of gas nozzles 140 a,b,c,d for a predefined timeperiod, and thereafter, stops the flow of process gas through the gasnozzle(s). Thereafter, the gas flow controller 100 regulates the flow ofprocess gas through another gas nozzle (or another set of gas nozzles)for another time period, and then stops the flow of process gas throughthat gas nozzle, and so on. The starting and stopping of gas flowthrough the gas nozzles 140 is repeated at least once, and morepreferably, a multitude of times, during processing of the substrate 50.For example, the gas flow controller 100 activates the gas flow valves150 on one gas nozzle to flow gas into the chamber 25 for about 1 toabout 50 seconds, shuts off the flow valve for 1 to 50 seconds, and thenturns back on the gas flow for about 1 to about 50 seconds, and so on.Preferably, the pulsed bursts of process gas into the chamber areprovided through an individual or sets of gas nozzles 140 that arepositioned around the periphery of the substrate 50, a suitable numberof gas nozzles comprising from two to eight gas nozzles, and morepreferably, four to six gas nozzles that are uniformly spaced apart inthe chamber 25.

By sequentially, or in an overlapping manner, turning on and off the gasflows to various gas nozzles 140 positioned around the circumference ofthe chamber 25, the distribution and flow pattern of process gas speciesin the chamber 25 is controlled in a predetermined manner. Furthercontrol over the distribution of gas in the chamber is possible byvarying the flow rates of the process gas injected through each gasnozzle 140, the time period for which the process gas flows throughparticular gas nozzles 140, and the timed sequence of process gas flowthrough a set of gas nozzles 140 in relation to the position of the gasnozzles in the chamber. Each sequence of process gas flow through a setof gas nozzles 140 forms a process cycle, and the process cycles arerepeated multiple times during processing of a single substrate 50.Typically, in each process cycle, process gas is introduced through agas nozzle for a period of from about 1 to about 10 seconds, and morepreferably, a period of from about 1 to about 5 seconds. The number ofcycles is based on the total process time desired. For example, if theprocess gas is introduced into each gas nozzle for 2 seconds only, andthe total substrate process time to completion is 40 seconds, a total ofabout 5 cycles are to be performed, each cycle providing process gas forabout 8 seconds into the chamber 25.

FIGS. 3a to 3 c illustrate exemplary different process gas flow timingsequences for actuating sets of gas nozzles 140 in the chamber 25. Thesefigures are graphical representations of the timing sequence, or theperiod of duration of the opening and closing of each valve 150 thatsupplies process gas to one of four gas nozzles 140 positionedcircumferentially along the sidewalls of the chamber 25. A gas flowvalve 150 of a particular gas nozzle 140 is opened for a predefinedperiod of, for example, 10 seconds, to provide a source of process gasinto the chamber 25, and thereafter, the gas flow valve is shut off, andanother gas flow valve is turned on to provide another source of processgas into the chamber. The gas flow timing cycle of FIG. 3a comprises afirst cycle comprising four steps in which process gas is firstintroduced through a first gas nozzle 140, and then sequentially flowedthrough each of the second, third, and fourth gas nozzle to complete thecycle. The timed sequence of operation of the gas flow valves 150 issuch that the source or ingress of the gas flow into the chamber 25appears to rotates around a central longitudinal axis of the chamber 25along the circumference of the process chamber. The adjacent gas nozzles140 can be turned on and off to provide an apparent rotating gas sourcethat moves in a clockwise or counter-clockwise. Alternatively, the flowof process gas can be pulsed in a different sequence of gas nozzles, orin an overlapping sequence of gas nozzles, from one gas nozzle toanother gas nozzle around the circumference of the chamber 25. Forexample, in a typical overlapping sequence, gas nozzle 1 is opened toflow process gas into the chamber 25, and before gas nozzle 1 is closed,adjacent gas nozzle 2 is opened and only after gas nozzle 2 is open fora predefined overlapping time, is gas nozzle 1 shut off. Thereafter, gasnozzle 3 is opened while gas nozzle 2 is still open, and then gas nozzle2 is shut off, and so on, to provide a rotating and overlapping timingsequence of pulsed gas sources around the circumference of the chamber25.

In another preferred embodiment, illustrated in FIG. 3b, the gas flowcontroller 100 alternates the flow of the first and second process gasstreams between a pair of facing gas nozzles 140 that face one other atone location in the process chamber 25 to another pair of facing gasnozzles 140 that face each other at another location in the processchamber 25. In this version, the gas flow is initially provided througha leading pair of first and second gas nozzles 140 a,b that face oneanother. Before or after turning off the flow of gas through the leadingpair of gas nozzles 140 a,b, the gas flow through a secondary pair ofgas nozzles 140 c,d is turned on, allowing process gas to flow into thechamber 25 from another pair of gas injections nozzles 140 c,d at adifferent location in the chamber 25. Preferably, the gas distributor 90comprises at least two pairs of nozzles that are located 90° apart alonga perimeter of the chamber 25, each pair of nozzles opposing and facingeach other. Each gas nozzle 140 a,b of a facing pair of nozzles isturned on simultaneously to provide first and second gas flow streamsinjected through a facing pair of gas nozzles 140 a,b and then turnedoff. Thereafter, each gas nozzle 140 c,d of a second pair of facing gasnozzles is turned on, and thereafter turned off. Thus the two pairs ofgas nozzles 140 a,b and 140 c,d are sequentially actuated to providepulsed bursts of process gas from process gas sources that are locatedon two lines cutting across the chamber 25 at right angles to oneanother. For example, as shown in FIG. 3b, the gas nozzles 1 and 3 areopened simultaneously for a first time period T of about 0<T<10 seconds,and gas nozzles 2 and 4 are opened simultaneously for a second timeperiod T of about 10<T<20 seconds. Alternatively, as shown in FIG. 3c,two adjacent gas nozzles 140 which are 90° apart can also besimultaneously opened to supply process gas through adjacent pairs ofgas nozzles, instead of through pairs of facing gas nozzles. Any otheroperative combination of facing or adjacent gas nozzles is also withinthe scope of the present invention, as would be apparent to one ofordinary skill.

The timing sequence of flowing process gas through various gas nozzles140 can also be regulated to control the gas flow path or flow patternin the chamber 25. Turning on and off a series of gas nozzles 140positioned around the chamber 25, effectively changes the location ofingress of the gas into the chamber 25 to different positions along thecircumference of the chamber 25. For example, gas streams can beinjected through one or more nozzles 140 located at one position in thechamber 25, and thereafter, gas streams can be injected through othergas nozzles 140 located at a different position in the chamber 25. Gasflow streams injected through pairs of facing gas nozzles 140 a,b strikeone another and coalesce to form an upwardly directed stream of gas,that upon impinging on the dome shaped ceiling 40 is redirected towardthe periphery of the substrate 50. The resultant flow of gas that movesvertically up along the center of the chamber 25 and along sidewalls 30of the process chamber 25 has been found to significantly improve theprocess etching uniformity, especially when the gas stream rotatesaround different positions along the circumference of the chamber 25.

The pulsed flow of gas is particularly suitable for introducing etchinggas into etching chambers 25 for etching the substrate 50 because itprovides more uniform etching rates across the surface of the substrate50. In particular, the rotating gas inlet source has been found tosignificantly improve the process etching uniformity. For example, apreferred sequence of gas flow pulses for an etching process conductedwith four gas nozzles 140 around the substrate 50 comprises thefollowing steps: (i) gas nozzle 1 turned on for 2 seconds and stopped,(ii) gas nozzle 2 turned on for 2 seconds and stopped, (iii) gas nozzle3 turned on for 2 seconds and stopped, (iv) gas nozzle 4 turned on for 2seconds and stopped, and (v) optional repetition of these steps for oneor more cycles until the substrate is processed. Other gas flowsequences can also use pulsed gas bursts of from 0.1 to 2.5 secondsdepending on the processing type and the number of gas nozzles.

In the embodiments described above, a computer controller system 145preferably operates the process chamber 25 and gas nozzles 140. Thecomputer controller system comprises a computer program code productthat controls a computer comprising one or more central processor units(CPUs) interconnected to a memory system with peripheral controlcomponents, such as for example, a PENTIUM microprocessor, commerciallyavailable from Intel Corporation, Santa Clara, Calif. The CPUs of thecomputer controller system 145 can also comprise ASIC (applicationspecific integrated circuits) that operate a particular component of thechamber 25, such as the gas nozzles 140. The interface between anoperator and the computer system 145 is typically a video monitor 155and a light pen 160. To select a particular screen or function, theoperator touches a designated area of a screen displayed on the CRTmonitor 155 with the light pen 160 and pushes the button on the pen. Thearea touched changes its color, or a new menu or screen is displayed,confirming the communication between the light pen 160 and the CRTmonitor 155. Other devices, such as a keyboard, mouse, or pointingcommunication device can also be used to allow the user to communicatewith the computer controller system 145.

The computer program code for operating the CPU(s) and other devices ofthe computer controller system can be written in any conventionalcomputer readable programming language, such as for example, assemblylanguage, C, C⁺⁺, or Pascal. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor andstored or embodied in a computer-usable medium, such as a memory systemof the computer controller system 145. If the entered code text is in ahigh level language, the code is compiled to a compiler code which islinked with an object code of precompiled windows library routines. Toexecute the linked and compiled object code, the system user invokes theobject code, causing the computer to load the code in memory system toperform the tasks identified in the computer program code.

The computer program code comprises one or more sets of computerinstructions that operate the timing, process gas composition, chamberpressure, substrate temperature, RF power levels, and other parametersof the process recipe being performed in the process chamber 25. Thecomputer program code also comprises computer instructions code foroperating the gas flow distributor system 90, including the operationsof turning on/off the gas nozzles, controlling the timing sequence ofthe gas nozzles, and controlling operation of a gas flow controller 100to control the flow rates of the process gas through the gas nozzles140.

A preferred version of the computer program code, as illustrated in FIG.4, comprises multiple sets of program code, such as program code 175that allows an operator to enter or select a process recipe, and thatexecutes operation of the process recipe in a selected process chamber25, chamber manager program code 180 for operating and managingpriorities of the chamber components in the process chamber 25, and gasflow controller program code 185 for operating the gas nozzles 140.While illustrated as separate program codes that perform a set of tasks,it should be understood that these program codes can be integrated, orthe tasks of one program code integrated with the tasks of anotherprogram code to provide a desired set of tasks. Thus the computercontroller system 145 and computer program code described herein shouldnot be limited to the specific embodiment of the program codes describedherein, and other sets of program code or computer instructions thatperform equivalent functions are within the scope of the presentinvention.

In operation, a user enters a process set and process chamber numberinto the process selector program code 175 via the light pen 160 and CRTmonitor 155. The process sets are composed of process parameters neededto carry out a specific process recipe in the chamber 25 and the processsets are identified by predefined set numbers. The process selectorprogram code 175 identifies a desired process chamber 25 and set ofprocess parameters to operate the process chamber for performing aparticular process. The process parameters include process conditions,such as for example, chamber temperature and pressure, gas energizerparameters such as microwave or RF bias power levels and magnetic fieldpower levels, cooling gas pressure, and chamber wall temperature. Theprocess conditions also include gas composition, flow rates, and gasvalve timing sequence that sets the timing of the flow valves 150 of thegas nozzles 140. The timing sequence is stored in a table of timinginstructions that lists the timing intervals inputted by the operator,or contains an algorithm for timing the actuation (turn on) orde-actuation (turn off) sequence of the flow valves 150 in thepredetermined sequential order of operation.

The process selector program code 175 executes the process set bypassing the particular process set parameters to the chamber managerprogram code 180 which control multiple processing tasks in differentprocess chambers according to the process set determined by the processselector program code 175. For example, the chamber manager program code180 comprises program code for etching a substrate or depositingmaterial on a substrate in the chamber 25. The chamber manager programcode 180 controls execution of various chamber components through codeinstruction sets which control operation of the chamber components.

Examples of chamber component code instruction sets include a substratepositioning instruction set 190 that controls robot components that loadand remove the substrate onto the support 45, process gas controlinstruction set 195 that controls the composition and flow rates ofprocess gas supplied into the chamber 25, a pressure control instructionset 200 that controls the size of the opening of the throttle valve 125,a gas energizer control instruction set 205 that controls the powerlevel of the gas energizer 72. In addition, a gas flow controllerprogram code 185 operates the gas distributor 90 to control the flow ofprocess gas into the process chamber. In operation, the chamber managerprogram code 180 selectively calls the chamber component instructionsets in accordance with the particular process set being executed,schedules the chamber component instruction sets, monitors operation ofthe various chamber components, determines which component needs to beoperated based on the process parameters for the process set to beexecuted, and causes execution of a chamber component instruction setresponsive to the monitoring and determining steps.

The gas flow controller program code 185 comprises a flow valveinstruction set 210 for controlling each flow valve 150 in the gasconduit to a gas nozzle 140, and a sequence timing instruction set 215for timing the sequence of opening and closing of the flow valves 150.While described as separate instruction sets for performing a set oftasks, it should be understood that each of these instruction sets canbe integrated with one another, or the tasks of one set of program codeintegrated with the tasks of another to perform the desired set oftasks. Thus, the computer system 145 and the computer program codedescribed herein should not be limited to the specific embodiment of thefunctional routines described herein; and any other set of routines ormerged program code that perform equivalent sets of functions are alsoin the scope of the present invention.

The flow valve instruction set 210 actuates (turns on) the gas flowvalve 150 of a single gas nozzle 140 to flow gas therethrough, or morepreferably, simultaneously actuates a pair of gas nozzles 140 a,b thatface one another to flow gas simultaneously through both the facing gasnozzles. Preferably, the flow valve instruction set 210 actuates a gasflow valve 150 of a particular gas nozzle 140 for a short time periodthat is less than the time period required to process a particularsubstrate 50 in the chamber 25, to flow a pulsed burst of process gasinto the chamber 25. More preferably, the flow valve instruction set 210simultaneously actuates flow valves of a pair of facing gas nozzles 140a,b for a short time period to flow a first burst of gas through a pairof facing gas nozzles located at one position in the chamber 25, andthereafter, flows a second burst of gas through another pair of gasnozzles 140 c,d located at a different position in the chamber, asdescribed above.

The sequence timing instruction set 215 sets the timing of the flowvalves 150 from a table of sequenced timing instructions and timingintervals entered by the operator into the process selector programcode, or an algorithm for timing the actuation (turn on) andde-actuation (turn off) sequence of the flow valves 150 in the desiredpredetermined sequential order of operation of each valve. Each gas flowvalve 150 feeding a particular gas nozzle 140 is identifiable by aparticular number for the operator to program a predetermined timingsequence. The sequence timing instruction set 215 comprises code adaptedfor (i) flowing process gas through a first pair of gas nozzles 140 a,bfor a predetermined time period and thereafter stopping the flow ofprocess gas through the first pair of gas nozzles, and (ii) flowing gasthrough the second pair of gas nozzles 140 c,d for another predeterminedtime period and thereafter stopping the flow of process gas through thesecond pair of gas nozzles. The sequence timing instruction set 215repeats steps (i) and (ii) at least once to time the operation of thegas flow valves 150 in the desired predetermined sequence.

EXAMPLES

The following examples, illustrated in FIGS. 5a through 7 b, demonstratethat the process chamber 25 and gas flow distributor 90 of the presentinvention is capable of providing a uniform distribution of gaseousspecies and gas flow pattern across the surface of the substrate. Inthese examples, the chamber 25 comprising four gas nozzles 140positioned along the sidewalls 30 of the chamber 25, and equally spacedapart at 90° from each other. In these tests, a blanket layer ofaluminum deposited to a thickness of about 10,000 Å on the substrate wasetched. FIGS. 5a through 7 b illustrate the results of three separatetests in which the angle of the gas nozzles 140 relative to the surfaceof the substrate 50 was held at 45°, 60°, and 75°, respectively. Theetching gas comprised Cl₂, BCl₃, and N₂; the pressure in the chamber 25was ˜10 mTorr; and the temperature of the chamber 25 was maintained at80° C. The etching gas was pulsed through the gas nozzles 140 in thefollowing sequence (i) facing gas nozzles 1 and 3 turned on for 2 secand then turned off, (ii) facing gas nozzles 2 and 4 turned on for 2 secand then turned off. Thereafter, steps (i) and (ii) were repeated atotal of 20 process cycles to provide a cumulative processing time ofabout 40 seconds.

FIG. 5a is a contour map of a substrate surface showing contour lines ofthe amount of etching (representative of the etching gradient) of thesurface of the blanket layer of aluminum processed in a process chamber25 having gas nozzles 140 that injected gas into the chamber at aninclination angle of 45°. Each contour line represents a particularthickness of residual aluminum remaining after etching, that ranged from2823 Å to 3276 Å. The average thickness of the aluminum etched was about3093 Å. For a chamber having gas nozzles 140 inclined at an angle of45°, an etch rate variation of 10.8% with a standard deviation of 1σacross the substrate 50 represents significantly improved uniformity inetching rates across the substrate, as compared to the prior art. FIG.5b is a three-dimensional profile of the contour map of FIG. 5a, withthe Z-axis representing the etching rates across the surface of thesubstrate 50, showing slightly higher etch rates along a periphery ofthe substrate.

The contour map of FIG. 6a shows even greater improvement in etchinguniformity in a chamber 25 in which the gas nozzles 140 direct processgas streams toward the curved ceiling 40 at an angle of inclination of60° relative to the plane of the substrate 50. The thickness of theresidual aluminum remaining after etching ranged from 3243 Å to 3899 Åwith an average thickness of about 3590 Å. The etching rate variedacross the substrate 50 by a 1σ deviation, and the percent change inetching rates was about 4.831%, as compared to a la etching uniformityof 20% for traditional chamber designs having gas nozzles that flow gasin a horizontal or vertical flow path. FIG. 6b shows a three-dimensionalview of FIG. 6a, with the Z-axis representing the etching rate acrossthe substrate 50. From the depression in the middle of FIG. 6b, it isseen that slightly higher etch rates were obtained at the periphery ofthe substrate 50.

The contour map of FIG. 7a represents etch gradient lines of the etchedtopography surface of the blanket layer of aluminum layer in the chamber25 in which the gas nozzles 140 were inclined at an angle of 75°. Thethickness of the residual aluminum layer remaining after etching rangedfrom 3051 Å to 3699 Å with an average thickness of about 3386 Å. It isseen that la etching uniformity of 3.578% was obtained. FIG. 7b shows athree-dimensional view of FIG. 7b, with the Z-axis representing theetching rate across the substrate 50, showing superior uniformity andetching rates.

The gas distributor 90 and chamber of the present invention providesignificantly improved processing, as illustrated for processes foretching aluminum layers on substrates 50. The novel gas flowdistributors provide directional gas streams that result in a moreuniform distribution of gaseous species in the chamber 25, therebysignificantly enhancing processing uniformity. Furthermore, the flow ofprocess gas across the substrate 50 and chamber walls reduces gasstagnation regions, gas phase nucleation of undesirable species, anddeposition of excessive etchant residues on the sidewalls 30 andcomponents of the chamber 25. The gas flow stream in the chamber hasalso been found to more efficiently utilize the process gas in thechamber 25, thereby reducing the volume of gas that is used to process asubstrate 50, and decreasing concentration of undesirable gaseoushazardous and toxic gaseous species in the effluent.

Although the present invention has been described in considerable detailwith regard to the preferred versions thereof, other versions arepossible. For example, the location of the gas nozzles 140 be varied asapparent to one of ordinary skill. For example, the gas nozzles 140 canextend through the ceiling 40 or from the bottom wall around theperiphery of the substrate. Also, the number and position of the gasnozzles 140 can be arranged to provide the desired gas flow pattern inthe chamber 25, depending on the relative size of the substrate 50 andchamber 25. Furthermore, upper, lower, center, ceiling 40, base, floor,and other such terms of spatial orientation or structures can be changedto equivalent or opposite orientations without affecting the scope ofthe present invention. Therefore, the appended claims should not belimited to the description of the preferred versions contained herein.

What is claimed is:
 1. A substrate processing method comprising: (a)supporting a substrate in a process zone of a chamber having a surfaceabove the process zone; (b) directing a flow of process gas against thesurface above the process zone; (c) energizing the process gas; and (d)exhausting the process gas from the process zone.
 2. A method accordingto claim 1 wherein the surface above the process zone is dome shaped. 3.A substrate processing method comprising: (a) supporting a substrate ina process zone of a chamber having a surface adjacent the process zone;(b) introducing process gas at an inclined angle relative to thesubstrate to direct a flow of the process gas toward the surfaceadjacent the process zone; (c) energizing the process gas; and (d)exhausting the process gas from the process zone.
 4. A method accordingto claim 3 comprising introducing the process gas at an inclined angleof from about 30 to about 80 degrees relative to the substrate.
 5. Amethod according to claim 3 wherein (a) comprises supporting thesubstrate in a chamber having a surface above the process zone.
 6. Amethod according to claim 3 wherein (a) comprises supporting thesubstrate in a chamber having a dome shaped surface adjacent the processzone.
 7. A method according to claim 3 wherein introducing the processgas comprises introducing the process gas through a plurality ofoutlets.
 8. A method according to claim 7 wherein introducing theprocess gas comprises introducing the process gas at an anglesufficiently large to cause two streams of process gas to impingeagainst one another.
 9. A substrate processing method comprising: (a)supporting a substrate in a process zone; (b) introducing process gasthrough a plurality of outlets at an upwardly inclined angle relative tothe substrate, the inclined angle being sufficiently large to allow twostreams of process gas to impinge against one another; (c) energizingthe process gas; and (d) exhausting the process gas from the processzone.
 10. A method according to claim 9 wherein (a) comprises supportingthe substrate in a chamber having a surface adjacent to the processzone, and wherein (b) comprises directing the process gas against thesurface adjacent to the process zone.
 11. A method according to claim 10wherein the step of directing the process gas against the surfaceadjacent the process zone comprises directing the process gas against adome shaped surface adjacent the process zone.
 12. A method according toclaim 9 comprising introducing the process gas at an inclined angle offrom about 30 to about 80 degrees relative to the substrate.
 13. Amethod according to claim 9 comprising alternating the flow of gasbetween different outlets of the plurality of outlets.
 14. A methodaccording to claim 9 wherein (b) comprises introducing the process gasthrough a plurality of outlets that are above the substrate.
 15. Asubstrate processing method comprising: (a) supporting a substrate in aprocess zone; (b) introducing process gas through a first outlet at anupwardly inclined angle relative to the substrate and through a secondoutlet angled relative to the first outlet; (c) energizing the processgas; and (d) exhausting the process gas from the process zone.
 16. Amethod according to claim 15 wherein (b) comprises introducing theprocess gas substantially parallel to the substrate through the secondoutlet.
 17. A method according to claim 15 comprising introducing theprocess gas through the first outlet at an inclined angle of from about30 to about 80 degrees relative to the substrate.
 18. A method accordingto claim 15 wherein (b) comprises introducing the process gas through aplurality of first and second outlets.
 19. A method according to claim18 wherein (b) comprises introducing the process gas through the firstoutlets at an angle sufficiently large to cause two streams of processgas to impinge against one another.
 20. A substrate processing methodcomprising: (a) supporting a substrate in a process zone; (b)introducing process gas at an upwardly inclined angle relative to thesubstrate from above the substrate; (c) energizing the process gas; and(d) exhausting the process gas from the process zone.
 21. A methodaccording to claim 20 comprising introducing the process gas at aninclined angle of from about 30 to about 80 degrees relative to thesubstrate.
 22. A method according to claim 20 wherein (a) comprisessupporting the substrate in a process zone of a chamber having a surfaceadjacent to the process zone, and wherein (b) comprises introducing theprocess gas to direct a flow of process gas against the surface adjacentto the process zone.
 23. A method according to claim 22 wherein (a)comprises supporting the substrate in a process zone of a chamber havinga dome shaped surface adjacent to the process zone, and wherein (b)comprises introducing the process gas to direct the flow of the processgas against the dome shaped adjacent surface.
 24. A method according toclaim 20 wherein (b) comprises introducing the process gas through aplurality of outlets.
 25. A method according to claim 24 comprisingintroducing the process gas at an angle sufficiently large to cause twostreams of process gas to impinge against one another.
 26. A substrateprocessing method comprising: (a) supporting a substrate in a processzone; (b) introducing process gas by alternating a flow of the processgas through a plurality of outlets; (c) energizing the process gas; and(d) exhausting the process gas from the process zone.
 27. A methodaccording to claim 26 wherein (b) comprises introducing the process gasthrough a pair of facing outlets.
 28. A method according to claim 26comprising introducing the process gas at an inclined angle relative tothe substrate.
 29. A method according to claim 26 wherein (a) comprisessupporting the substrate in a process zone of a chamber having a surfaceadjacent the process zone, and wherein (b) comprises introducing theprocess gas at an inclined angle relative to the substrate to direct aflow of process gas against the surface adjacent the process zone.
 30. Amethod according to claim 29 wherein (a) comprises supporting thesubstrate in a chamber having the surface above the process zone.
 31. Amethod according to claim 30 comprising introducing the process gas atan inclined angle relative to the substrate to direct the flow of theprocess gas against a surface adjacent the process zone that is domeshaped.
 32. A method according to claim 26 comprising introducing theprocess gas so that two streams of process gas impinge against oneanother.
 33. A method according to claim 32 comprising introducing theprocess gas at an inclined angle relative to the substrate.
 34. Asubstrate processing method comprising: (a) supporting a substrate in aprocess zone; (b) introducing a first burst of process gas into theprocess zone through a first nozzle and energizing the process gas; and(c) introducing a second burst of process gas into the process zonethrough a second gas nozzle while continuing to energize the processgas.
 35. A method according to claim 34 further comprising repeatingsteps (b) and (c) at least once.
 36. A method according to claim 34wherein introducing the first and second bursts of process gas comprisesintroducing the first and second bursts of process gas at an inclinedangle of from about 30 to about 80° relative to the substrate.
 37. Amethod according to claim 34 comprising supporting the substrate in aprocess zone of a chamber having a curved surface adjacent to theprocess zone, and further comprising introducing the first and secondburst of process gas by directing the process gas against the curvedsurface.